BOSTON (AP) – The “stem-to-stern” Big Dig review Gov. Mitt Romney ordered after a fatal tunnel collapse last summer has found the highways, tunnels and bridges in downtown Boston are well built overall, but some repairs are urgently needed.

Romney, presenting the final results of the 90-day, $4.5 million review, said Friday the Central Artery project’s original fire detection system is not being used because it was responding too slowly to temperature increases. Instead, tunnel operators are spotting fires by relying on cell phone calls from motorists or by noticing a reduction in their speed as they slam on their brakes when they see a fire.

Romney said that system is unreliable because the Dig doesn’t have full cell service and the speed-detection system can’t be completely monitored.

In addition, the governor said the $14.6 billion dollar project’s Operations Control Center in South Boston – which houses those workers expected to spot fires and other problems – has lost power twice since the July 10 accident that killed 39-year-old Milena Del Valle of Boston. That has left tunnel operators completely in the dark for 15 minutes or more.

The workers did not have flashlights because they were considered unnecessary with the backup systems. Romney said a computer software glitch, now being fixed, prevented an immediate switch to battery power and then backup generators.

“The total story is this: In the opinion of the experts, the Central Artery system is fundamentally safe, but there are corrective actions to be taken,” Romney said during a Statehouse news conference.

The problems he identified will have to be repaired after he leaves office in January. Romney said he expects most of the bills to paid by whomever investigators determine was at fault. A criminal investigation is under way into the death of Del Valle, who was crushed by 12 tons of falling ceiling tiles.

Despite the concerns, the governor said he feels much more confident driving around Boston than in July, when he ordered the review of every road, bridge and operational system that’s part of the Metropolitan Highway System.

At the time, he accused the project overseer, Bechtel/Parsons Brinckerhoff, of shoddy workmanship.

“I must admit that when the ceiling panel fell, my reaction was, “What in the world are we going to find when we open Pandora’s box, how many things are we going to find where there was real shoddy either design or construction?”‘ Romney said. “And I must admit that I am, at this stage, by virtue of this view, a good deal more confident that the tunnel and Artery system is safe than I was 90 days ago.”

During a preliminary briefing on Sept. 26, Romney said the inspectors had found extensive deterioration in the Sumner Tunnel’s concrete ceiling. He said those repairs, as well as repairs to the Callahan Tunnel, will have to be completed immediately after the Central Artery tunnels are repaired.

The recently concluded safety review was primarily conducted by more than 40 engineers from an Illinois consulting firm, Wiss, Janney, Elstner Associates Inc., and Schirmer Engineering Corp. of Chicago.

They examined 29 miles of tunnel ceiling panels, 200,000 feet of concrete and steel-box girders – which form the roadway floor – and some 2,800 metal poles, 62 buildings and over 20 life safety systems such as fire detection and emergency ventilation.

Romney said they found the system to be fundamentally sound, but not without problems. In some cases, there were as small as a corroded light fixture holding a strobe light next to an emergency exit. In other cases, they were more significant, such as a bend in a bracket holding a cable to the Dig’s signature landmark, the Leonard Zakim Bridge. The cable itself holds back 1 million pounds of pressure.

“It shouldn’t be bent at all,” the governor said. “It should be absolutely flush, and it’s bent, and the question is, “Why?”‘

The inspectors also found numerous concrete problems, including cracking in supports. In addition, they questioned whether channels holding steel road reinforcements had been properly filled with grout, a problem identified and supposedly fixed during construction.

Romney said he considered the most troubling finding to be a lack of a “comprehensive, regular inspection program.”

Nonetheless, Gary Klein, the Wiss, Janney engineer who led the review, said motorists should be reassured.

“You’ve seen some slides of some pretty ugly conditions, so to speak,” he said after Romney completed his PowerPoint presentation. “It was our job to point those out. What we didn’t show you were the miles and miles of box girders, roadway surfaces and tunnels that looked absolutely pristine, so you can get a bit of a stilted picture here.”

During the briefing, the governor also announced that repairs to the Interstate 90 connector tunnels where Del Valle was killed are fully complete on the westbound side, and 95 percent complete heading eastbound. But he said the state is still awaiting approval from the Federal Highway Administration before reopening them.